Views: 0 Author: Site Editor Publish Time: 2026-05-19 Origin: Site
Selecting an AHU for a hospital operating room (OR) hinges on infection control, ultra-clean air, precise temperature/humidity, positive pressure, redundancy, and low noise—far stricter than standard comfort AHUs.
1. Understand Core OR Requirements (Non-Negotiable)
Air Changes (ACH) & Fresh Air
Minimum 20 ACH total (ASHRAE 170); 25–30 ACH typical.
≥4 ACH outdoor air (dilute anesthetic gases, microbes).
Temperature & Humidity
Temp: 20–24°C (68–75°F).
RH: 30–60% (prevent static, infection; avoid <20% or >60%).
Pressure Cascade (Critical for Contamination Control)
OR > Anteroom > Corridor: +5–+10 Pa (OR relative to corridor).
Positive pressure 24/7; no negative pressure during surgery.
Cleanliness (ISO 14644)
ISO 7 (Class 10,000) at rest; ISO 6 (Class 1,000) during surgery.
Noise & Vibration
≤35–40 dB(A) at 1 m (no interference with communication/equipment).
Vibration isolation (spring/rubber mounts; flexible duct connectors).
2. Filtration Selection (Multi-Stage, HEPA-Centric)
OR AHUs require 4–5 stage filtration to meet ISO 6–7:
Stage | Grade | Efficiency | Purpose |
|---|---|---|---|
Pre-filter | G4/MERV 7 | ≥90% @ 5 μm | Protects coils/downstream filters |
Medium | F8/MERV 14 | ≥90% @ 1 μm | Removes fine particles/microbes |
Sub-HEPA | H13 | ≥99.95% @ 0.3 μm | Final AHU filtration |
Terminal HEPA | H14/ULPA | ≥99.995% @ 0.3 μm | At supply diffusers (ISO 6) |
3. AHU Type & Configuration
Unit Type
Horizontal, double-skin, stainless steel (304/316L) (corrosion resistance for frequent disinfection).
Modular, airtight casing (low leakage <1%; rigid frame to reduce vibration noise).
Internal acoustic lining (25–50 mm PU/glass wool; ≤38 dB(A)).
Air Handling Sections (Standard OR AHU Layout)
Outdoor air intake (high-mounted, away from exhausts/pollutants).
Pre-filter (G4)
Mixing box (outdoor + return air)
Cooling coil (chilled water) (dehumidify; ≤2 m/s face velocity to avoid carryover).
Heating coil (hot water/steam) (reheat to 20–24°C).
Humidifier (dry steam only; no water spray—prevents microbial growth).
Medium filter (F8/MERV 14)
EC fan section (direct-drive, no belts; low noise 3–5 dB; VFD for airflow control).
Sub-HEPA (H13)
Supply plenum (to terminal H14 HEPA diffusers in OR)
4. Fan Selection (Low Noise, High Static, Redundancy)
Type: EC/outer-rotor centrifugal, direct-drive (no belt noise/wear; 30%+ energy savings).
Static Pressure: 400–800 Pa (overcome filters, coils, ductwork, terminal HEPA).
Redundancy: N+1 or 2N (backup fan with auto-failover; no downtime during surgery).
Balancing: Dynamic + static balancing; spring/rubber isolators (≤2 mm/s vibration).
5. Redundancy & Controls (24/7 Reliability)
System Redundancy
Dual fans, dual coils, dual filters (auto-switch on failure).
Independent backup AHU for critical ORs (I–II 级).
Precision Controls
DDC (Direct Digital Control) with real-time monitoring:
Temp: ±0.5°C; RH: ±5%
Pressure: ±1 Pa (cascade control)
Airflow: ±5% (VFD fan speed control)
Filter differential pressure (alarm when clogged).
BMS integration (remote monitoring, data logging, alarm alerts).
6. Material & Construction (Anti-Microbial, Easy to Clean)
Casing: 304/316L stainless steel (resists disinfectants: bleach, alcohol, hydrogen peroxide).
Internal surfaces: Smooth, non-porous, no sharp edges (easy to wipe down; no dust/moisture accumulation).
Drainage: Positive condensate drain (anti-siphon; no direct connection to sewer—prevents backflow/contamination).
No stagnant zones: Sloped floors, rounded corners (prevents water pooling/bacterial growth).
